Phosphorus removal and recovery from polytetrahydrofuran wastewater by solventing-out crystallization

AbstractPhosphorus recovery through crystallization has been widely recommended for wastewater treatment. Polytetrahydrofuran wastewater was subjected to lab-based solventing-out crystallization to investigate methanol and ethanol as phosphorus recovery extractants. Extractant species, dosage, reaction time, and pH were measured to determine the optimum extractant and parameters for phosphorus recovery. The results show that the phosphorus recovery rates from raw wastewater were 88 and 93% with methanol and ethanol as extractants, respectively, at 30 mg/L extractant dosage, 2 h reaction time, and pH 6.7. Phosphorus recovery rate reached 99% under the following optimum reaction conditions: pH level, 9.0; optimum ethanol dosage, 20 mg/L; and reaction time, 5 min. The crystals were identified as Na2HPO4through X-ray diffraction, and 97% Na2HPO4mass fraction was detected through ion chromatography. Most crystals had no crystal water. Two ethanol recovery cycles were determined via the ethanol recovery experiment on the supernatant after crystallization.